This invention relates to methods of and apparatus for conveying randomly received items, such as rolls of toilet tissue or paper towels, and for placing these items on apparatus, such as an infeed flight conveyor for an overwrap machine or the like, which is continuously operable at a steady cycling rate.
In the manufacture of toilet tissue or paper towels, the paper is wound onto an elongate mandrel of cardboard tubing or the like to form a log approximately ten feet (3 m.) in length. These logs are then cut to form package-size rolls either by a slitter winder or by a roll saw. Typically, the rolls are then wrapped in an overwrap machine prior to being bulk-packed for shipment. Whether the rolls of towels or tissue are cut by a slitter winder or by a roll saw, the rolls are often intermittently and randomly delivered to the overwrap machine. Typically, overwrap machines operate most desirably if they are fed items operated at a steady and regular pace so as to achieve the high wrapping rate at lowest possible machine speed. It is usually preferred to operate overwrap machines continuously without skipping a wrapping cycle to provide the best possible operating efficiency of the machine. After skipping one or more wrapping cycles, registration problems often arise with the first item wrapped by the overwrap machine upon start up.
Usually an overwrap machine is fed items to be wrapped from more than one supply (i.e., from more than one slitter winder or log roll saw). Items may be fed to the overwrap machine from either one or the other of the supplies, or from both of the supplies simultaneously if, for example, a grouping of items are to be wrapped, or alternately from one supply and then the other. It has heretofore been a problem to balance the items in the various supplies so as to insure an adequate supply exists to feed the overwrap machine in the event the supply of items is momentarily interrupted or to prevent the backlog of items in the other supply from becoming excessive. It has also been a problem to form groupings (e.g., a 2.times.2 array of rolls of toilet tissue) of the items to be fed to the overwrap machine.
In some known item-conveying and pacing systems which randomly receive items and deliver them to a timed apparatus (e.g., a flight conveyor) rolls of paper towels or toilet tissue were abruptly stopped and started and were changed from one level to another. This sometimes resulted in the rolls becoming partially unrolled, thus making them difficult to wrap. Upon abruptly stopping and starting the rolls, certain of the known pacing conveyor systems caused the rolls to "telescope" (i.e., to cause the center of the roll and the roll case to project outwardly at one end of the roll and inwardly at the other end of the roll).
Reference may be made to the following U.S. Pat. Nos. which are in the same general field as the apparatus of this invention: 3,452,856, 3,459,289, 3,656,606, 3,794,154 and 3,938,650.
In several of the above-noted prior art references, conveying systems are disclosed which utilize a differential drive system responsive to an electric eye or other sensor which detected the position of an item relative to the flights of a flight conveyor and speeded up or slowed down one conveyor in the system relative to another conveyor so as to place the item at a desired location on the flight conveyor. These prior systems, however, required that the differential drive be operated on almost every cycle of the flight conveyor and the margin of error was, in many instances, small. This resulted in the conveyor system skipping placement of an item on the flight conveyor at relatively frequent intervals. Also, these prior art systems were not, for the most part, adapted to receive and feed items from a plurality of item sources or to form groupings of items to be wrapped.